Mains Supply Failure Alarm

Whenever AC mains supply fails, this circuit alerts you by sounding an alarm. It also provides a backup light to help you find your way to the torch or the generator key in the dark. The circuit is powered directly by a 9V PP3/6F22 compact battery. Pressing of switch S1 provides the 9V power supply to the circuit. A red LED (LED2), in conjunction with zener diode ZD1 (6V), is used to indicate the battery power level.

Resistor R9 limits the operating current (and hence the brightness) of LED2. When the battery voltage is 9V, LED2 glows with full intensity. As the battery voltage goes below 8V, the intensity of LED2 decreases and it glows very dimly. LED2 goes off when the battery voltage goes below 7.5V. Initially, in standby state, both the LEDs are off and the buzzer does not sound. The 230V AC mains is directly fed to mains-voltage detection optocoupler IC MCT2E (IC1) via resistors R1, R2 and R3, bridge rectifier BR1 and capacitor C1.

Illumination of the LED inside optocoupler IC1 activates its internal phototransistor and clock input pin 12 of IC2 (connected to 9V via N/C contact of relay RL1) is pulled low. Note that only one monostable of dual-monostable multivibrator IC CD4538 (IC2) is used here. When mains goes off, IC2 is triggered after a short duration determined by components C1, R4 and C3. Output pin 10 of IC2 goes high to forward bias relay driver transistor T1 via resistor R7.

Mains Supply Failure Alarm Circuit Diagram

Relay RL1 energises to activate the piezo buzzer via its N/O contact for the time-out period of the monostable multivibrator (approximately 17 minutes). At the same time, the N/C contact removes the positive supply to resistor R4. The time-out period of the monostable multivibrator is determined by R5 and C2. Simultaneously, output pin 9 of IC2 goes low and pnp transistor T2 gets forward biased to light up the white LED (LED1).

Light provided by this back-up LED is sufficient to search the torch or generator key. During the mono time-out period, the circuit can be switched off by opening switch S1. The ‘on’ period of the monostable multivibrator may be changed by changing the value of resistor R5 or capacitor C2. If mains doesn’t resume when the ‘on’ period of the monostable lapses, the timer is retriggered after a short delay determined by resistor R4 and C3.

Source: EFY Mag

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1 3 12 2 VDC Variable Power Supply

Power supply circuit to generate output below were variations between 1.3V DC to 12.2V DC with 1A current.

In addition, the power supply circuit is also equipped with over-current protection or shield against belebih flow. Power supply circuit is very simple, but the quality is quite good, made ​​her basiccally regulator IC LM723 is a fairly legendary.

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Simple Transformerless 5 Volt Power Supply

An increasing number of appliances draw a very small current from the power supply. If you need to design a mains powered device, you could generally choose between a linear and a switch-mode power supply. However, what if the appliance’s total power consumption is very small? Transformer-based power supplies are bulky, while the switchers are generally made to provide greater current output, with a significant increase in complexity, problems involving PCB layout and, inherently, reduced reliability. 

Is it possible to create a simple, minimum part-count mains (230 VAC primary) power supply, without transformers or coils, capable of delivering about 100 mA at, say, 5 V A general approach could be to employ a highly inefficient stabilizer that would rectify AC and, utilizing a zener diode to provide a 5.1 V output, dissipate all the excess from 5.1 V to (230×v2) volts in a resistor. Even if the load would require only about 10 mA, the loss would be approximately 3 watts, so a significant heat dissipation would occur even for such a small power consumption. 

At 100 mA, the useless dissipation would go over 30 W, making this scheme completely unacceptable. Power conversion efficiency is not a major consideration here; instead, the basic problem is how to reduce heavy dissipation and protect the components from burning out. The circuit shown here is one of the simplest ways to achieve the above goals in practice. A JVR varistor is used for overvoltage/surge protection. Voltage divider R1-R2 follows the rectified 230 V and, when it is high enough, T1 turns on and T3 cannot conduct.

Circuit diagram:

When the rectified voltage drops, T1 turns off and T3 starts to conduct current into the reservoir capacitor C1. The interception point (the moment when T1 turns off) is set by P1 (usually set to about 3k3), which controls the total output current capacity of the power supply: reducing P1 makes T1 react later, stopping T3 later, so more current is supplied, but with increased heat dissipation. Components T2, R3 and C2 form a typical ‘soft start’ circuit to reduce current spikes this is necessary in order to limit C1’s charging current when the power supply is initially turned on. At a given setting of P1, the output current through R5 is constant. 

Thus, load R4 takes as much current as it requires, while the rest goes through a zener diode, D5. Knowing the maximum current drawn by the load allows adjusting P1 to such a value as to provide a total current through R5 just 5 to 6 mA over the maximum required by the load. In this way, unnecessary dissipation is much reduced, with zener stabilization function preserved. Zener diode D5 also protects C1 from over voltages, thus enabling te use of low-cost 16 V electrolytics. 

The current flow through R5 and D5, even when the load is disconnected, prevents T3’s gate-source voltage from rising too much and causing damage to device. In addition, T1 need not be a high-voltage transistor, but its current gain should exceed 120 (e.g. BC546B, or even BC547C can be used).

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max output 1A Simple power supply variable Voltage 0 15V

Simple power supply variable Voltage 0-15V, max output 1A.
This circuit is simple, direct current power supply.It can adjust the voltage to 0-15Volt with rotating VR.And current is 1A.Using a transistor number 2N3055,It is used to boost up electrical current the output. For C1, C2, C3 for electric filtering the smooth up. This integrated circuit used for constant current.Q1 – 2N3055 should be taken with a heat sink. 

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L200 IC Circuit 3 to 30V Power Supply

 The following picture shown a 3 to 30V power supply circuit diagram using L200 IC made by Anwar von Sroka.It is constructed for the use with 100W transceivers.

The L200 IC which is known as virtually blow-out proof IC for voltage and current programmable regulation, is able for regulating the voltage as well as the current. It should be connected as close as possible to the minus terminal. Here, if you need to see the L200 datasheet.

Download this application datasheet about 3 to 30V Power Supply using L200 IC Circuit by Anwar von Sroka, here: http://www.mydarc.de/dl5dbm/20a_e.pdf

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MC1466L Power Supply 0 30V 0 2A

The basic requirements than one laboratorial power supply, it is to provide voltages and currents of operation that need the usual units, to have low output resistance, low noise, small ripple and good stabilisation. The above requirements are covered, from the circuit. Many power supply allocate electronic safety that him protects from destruction, when short their exit. In the circuit it can be regulated the superior price of output current, in a any price from 0 until 2A and him exceed, even if the load need has bigger requirements. Thus not only auto protection, but simultaneously it can it protects also the unit that it supplies, if the last one has the tendency to pull current bigger than forecasted. The circuit, it can be used still for the control of elements, the mapping out of characteristics of voltage /current and be used as a ideal source of constant voltage – current, capable it gives 0-30V dc and 0-2A, continuously regulated and no in steps. The transformer T1 has two secondary coils. The A coil supplies the circuit of output with high current, via the D1-4, C2 and the B coil, that it supplies the IC1, after is rectified by the D1, C4 and is stabilised by the D7, C5. The current passes through LED D6, who is also useful as clue of operation. The C7 makes compensation of frequency in the internal circuit of IC1 and the R2/D8/D9, him protects from the peaks voltage of network. With R3, we regulate the output voltage, in the point that we want. With the R8, we regulate the limit of current, that we wish in the exit. In the exit of power supply exists one multiple Darlington, constituted from the Q1, Q2 and Q3, Q4 that is parallel.The Resistances R14, R15 ensure the homology of currents of collector, the R10 until R12 improve the DC stability of output circuit, that has basic importance in high temperature, where the reverse currents begin to become considerable. The R9, c10, c11 achieves the compensation of frequency in the output amplifier of IC1 and the D13, his protection. Through the R19 it passes the output current. The fall of voltage that is presented in utmost his is degraded at a percentage and it is applied in the entry of 11 IC1. In the second entry of 10 IC1 is applied a constant voltage, the price of which is regulated by the R8, in the desirable biggest price of output current. As soon as the output current exceed this price, the fall of voltage in the R19, it is applied in the entry of 10 IC1, so that is activated the differential amplifier in the IC1 and it prohibits the further increase of output current. Capacitors C13, C14, C15 make unyoke of exit, while the D15 him protects from the reverse voltage. With instrument VA1, we can measure so much the output voltage, what the current, depending on the place that is placed switch S2. In the place that is appears in the circuit, the switch measure the current, taking sample from the fall of voltage, above in the R19, via the R17, R18. To we measure the voltage it will be supposed we move the switch in the other place, taking sample of output voltage. The micrometer regulation becomes from the R21, R22. The Transistor Q2, should be placed in a small heatsink, as well as the Q3, Q4, in heatsink with thermic resistance 2.6° C/W. The regulation of power supply can become easily, with the help of digital multimeter, which we will connect in the exit. Moving and regulating him trimmer in combination with main pontesometer regulation of voltage and current.

Part List

R1= 1.2Kohm 1W R20= 3.9Kohm D6= LED 5mm RED
R2-12= 100ohm R22= 56Kohm D7= 1N5252B
R3= 47Kohm Lin. C1-3= 330nF 250V D8= IN5236B
R4-7-21= 10Kohm trimmer C2= 4700uF 63V D9….14= 1N4002
R5= 8.2Kohm C4= 68uF 63V D15= MR501
R6-10= 12Kohm C5= 47uF 40V Q1= MPSL01
R8= 470ohm Lin. C6-15= 10nF 100V polyester Q2= 2N4923
R9= 1.2Kohm C7-12= 100nF 100V polyester Q3-4= 2N3055
R11= 820ohm C8= 680nF 100V polyester IC1= MC1466L Motorola
R13= 560ohm C9-14= 1uF 40V T1=220VAC/ A:34V/4A B:36V/50mA
R14-15= 0.68ohm 2W C10= 220pF ceramic F1= 1A/250V slow Fuse
R16= 330ohm C11= 10pF ceramic F2= 2A slow Fuse
R17= 470ohm C13= 220uF 40V S1= 2XON/OFF 10A/250V switch
R18= 470ohm trimmer D1-4= 15A Bridge S2= 2X2 ON 1A switch
R19= 0.22ohm 2W D5= 1N4002 VA1= 500μA

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